SILVER SPRING, MD—PRESS RELEASE—The U.S. Food and Drug Administration is alerting horse owners and veterinarians that one lot of a compounded combination drug product containing pyrimethamine and toltrazuril has been associated with adverse events in at least three horses. Two horses in Maine and one in Ohio ultimately died or were euthanized as a result.

The FDA recently finalized testing that revealed that this lot of product contained approximately 18 to 21 times the pyrimethamine indicated on the labeling. High doses of pyrimethamine can cause symptoms such as seizures, fever, and death.

Rapid Equine Solutions, LLC of Aston, PA, compounded the product, which was labeled as containing toltrazuril 416 mg/ml and pyrimethamine 17 mg/ml, packaged in 60 ml oral paste syringes for the treatment of the neurologic disease Equine Protozoal Myeloencephalitis (EPM). This product lot is accounted for and is no longer in distribution. The firm learned of the adverse events on May 24, 2019 and initiated a recall to the consumer/user level the same day.

The FDA is working with Rapid Equine Solutions and state partners to investigate these adverse events.

A previous incident linked to a different compounder also involved erroneously formulated compounded pyrimethamine/toltrazuril products that led to equine deaths. The previous incident occurred in 2014 and resulted in the deaths of four horses.

It is important to note that compounded products are not FDA-approved animal drugs. Additionally, toltrazuril is not FDA-approved for use in horses. The FDA has serious safety concerns about unapproved animal drugs, including certain compounded animal drugs, because they are of unknown quality have not been evaluated by the FDA for safety and effectiveness. Unapproved animal drugs also may not be labeled appropriately, which could potentially result in unsafe use of the product.

The FDA has approved several drug products for the treatment of EPM. Horse owners should consult their veterinarian for treatment advice.

The FDA encourages horse owners, caretakers and veterinarians to report adverse events to the FDA (such as seizure, fever, or collapse) in horses being treated with compounded pyrimethamine-containing products.

Owners and veterinarians can report complaints about animal drug products by following the instructions at: How to Report Animal Drug Side Effects and Product Problems.